As a refrigeration air conditioning hermetic compressor, there are conventional reciprocating type, rotary type and scroll type compressors, and these compressors are used in refrigeration or air conditioning fields of domestic or business purpose. Currently, compressors are developed while utilizing characteristics in terms of costs and performance.
Among them, a so-called hermetical compressor for preventing noise and eliminating the need of maintenance is a typical compressor in which a compressor mechanism and a motor are accommodated in a container, and a scroll compressor and a rotary compressor are in the mainstream. Generally, in the scroll compressor, a fixed scroll part in which a scroll lap rises from a mirror plate and an orbiting scroll part are meshed with each other to form a compression chamber therebetween, when the orbiting scroll part is allowed to orbit in a circular orbit while restraining the orbiting scroll part from rotating by a rotation-restraint mechanism, a compression chamber moves while changing its capacity, thereby carrying out the suction, compression and discharge, a predetermined back pressure is applied to an outer periphery of the orbiting scroll part and a back surface of a lap by lubricant oil, so that the orbiting scroll part is not separated from the fixed scroll part and does not flip over.
According to the conventional scroll, as shown in FIG. 17, a fixed scroll part 2 comprising a fixed lap 2a (lap 2a, hereinafter) and a fixed mirror plate 2b (mirror plate 2b, hereinafter) and an orbiting scroll part 4 comprising an orbiting lap 4a (lap 4a, hereinafter) and an orbiting mirror plate 4b (mirror plate 4b, hereinafter) are meshed with each other to form compression chambers 5 therebetween, and when the orbiting scroll part 4 is allowed to orbit in a circular orbit while restraining the orbiting scroll part 4 from rotating by a rotation-restraint mechanism 22, the compression chambers 5 move while changing capacity thereof, thereby carrying out suction, compression and discharge of refrigerant.
That is, the refrigerant is sucked into a suction pipe 1, passes through a suction space 3 of the fixed scroll part 2, and is enclosed in the compression chamber 5 formed between the fixed scroll part 2 and the orbiting scroll part 4, and compressed while reducing the capacity toward the center and is discharged from a discharge port 6.
At that time, the compression chambers 5 formed between the fixed scroll part 2 and the orbiting scroll part 4 are compressed and compression heat is generated. Thus, the scroll parts 2 and 4 are heated to high temperature by this heat. The pressures in the compression chambers 5 are gradually increased from the most outer peripheral compression chamber 5 toward the center compression chamber 5. Thus, temperature gradient is generated in the laps 2a and 4a from the most outer peripheral side toward the center. That is, the center (most inner peripheral side) compression chamber 5 is higher than the most outer peripheral compression chamber 5 in temperature. Due to this temperature rise, the laps 2a and 4a are thermally expanded, and especially inner peripheral ends of the laps 2a and 4a located on the center side which is heated to high temperature are largely thermally expanded. For this reason, when the laps 2a and 4a are thermally expanded, a gap in the thrust direction between teeth tips of the laps 2a and 4a and teeth bottoms of the mirror plates 2b and 4b becomes smaller than a gap at the time of assembling operation, and teeth tips of the laps 2a and 4a come into contact with the teeth bottoms of the mirror plates 2b and 4b. If the contact surface pressure is increased, there is a fear that galling is generated therebetween, and the mirror plates 2b and 4b and the laps 2a and 4a are damaged.
Hence, according to a scroll compressor described in patent document 1, a height of a lap of the orbiting scroll part or the fixed scroll part is adjusted between the teeth bottom to the teeth tip of the mirror plate, and a thrust direction gap is formed between the teeth tips of each lap to teeth bottoms of the other lap such that the gap becomes the greatest on the most inner peripheral side in the assembled state.
According to a scroll compressor described in patent document 2, a temperature distribution of surfaces of the teeth tips of the lap is measured, based on a result of the measurement, teeth tips of at least one of the lap of the orbiting scroll part or the fixed scroll part are formed such that the thrust direction gap between the teeth bottoms of the other lap becomes the greatest on the most inner peripheral side or the thrust direction gap is formed such that the gap is varied in a plurality of stages.
According to a scroll compressor described in patent document 3, as shown in FIG. 17, refrigerant gas sucked into the suction pipe 1 passes through the suction space 3 of the fixed scroll part 2 comprising the lap 2a and the mirror plate 2b, and is enclosed in the compression chamber 5 formed by meshing the fixed scroll part 2 with the orbiting scroll part 4 comprising the lap 4a and the mirror plate 4b, the refrigerant gas is compressed while reducing the capacity thereof toward the center of the fixed scroll part 2, and is discharged from the discharge port 6.
A back pressure chamber 8 is formed such as to be surrounded by the orbiting scroll part 4 and a sliding partition ring 17 mounted in a ring-like groove of a bearing member 7. The pressure in the back pressure chamber 8 is set to an intermediate pressure between discharge pressure and suction pressure, and the intermediate pressure is controlled such that this pressure becomes constant by a back pressure adjusting mechanism 9. The sliding partition ring 17 slides with a back surface 4d of the orbiting scroll part 4.
The back pressure adjusting mechanism 9 has a communication passage 10 which is in communication with a suction space 3 through the fixed scroll part 2 from the back pressure chamber 8, and the communication passage 10 is provided with a valve 11. If the pressure in the back pressure chamber 8 becomes higher than a set pressure, the valve 11 is opened, oil in the back pressure chamber 8 is supplied to the suction space 3, and the pressure in the back pressure chamber 8 is maintained at a constant intermediate pressure. The oil supplied to the suction space 3 moves to the compression chambers 5 together with the orbiting motion, and this prevents oil from leaking between the compression chambers 5. The intermediate pressure is applied to a back surface of the orbiting scroll part 4 to prevent the scroll compressor from flipping over. If the scroll compressor flips over, the fixed scroll part 2 and the orbiting scroll part 4 are separated, and oil leaks from that portion.
Iron-based material mainly comprising cast iron is used for the fixed scroll part 2 and the orbiting scroll part 4 which constitute the scroll compressor, or iron-based material is used for the fixed scroll part 2 and aluminum-based material is used for the orbiting scroll part 4.
(Patent Document 1)
Japanese Patent Application Laid-open No. S58-67902
(Patent Document 2)
Japanese Patent Application Laid-open No. H7-019891
(Patent Document 3)
Japanese Patent Application Laid-open No. 2001-280252
However, in the above structures, deformations of the fixed scroll part and orbiting scroll part caused by pressure are not taken into consideration, and when the scroll compressor is operated under high load or carbon dioxide is used as a refrigerant, the contact pressure acting on the teeth tips of the fixed scroll part and teeth bottoms of the orbiting scroll part becomes uneven, and there is a fear that galling or abnormal wearing is generated and there is a problem that the durability is deteriorated.
Hence, the present invention has been accomplished in view of the conventional problem, and it is an object of the invention to provide an efficient and reliable scroll compressor although the scroll compressor is simple and inexpensive.
When carbon dioxide is used as a refrigerant, the discharge pressure of the compressor on the high pressure side is higher than that of the conventional compressor by about 7 to 10 times. Thus, if a back pressure enough to prevent the orbiting scroll part from separating from the fixed scroll part is applied, the orbiting scroll part is strongly pushed against the fixed scroll part, abnormal wearing or seizing is generated, and performance is deteriorated by input increase.
In a system having large capacity and uses much refrigerant, at the time of transient operation wherein liquid refrigerant returns abruptly, shortage of lubricant oil or temperature rise is generated on a thrust surface of the orbiting scroll part due to carbon dioxide liquid refrigerant having high cleaning ability, and there is a fear that seizing is generated from the aluminum surface.
When both the scroll parts are made of metal, i.e., iron-based materials having the same coefficient of thermal expansion, since the gravity of the orbiting scroll part becomes great, centrifugal force at the time of operation is increased and as a result, a load of the bearing member is increased, and sliding loss is also increased. Especially when the scroll compressor is operated at high speed, since the centrifugal force is extremely increased, a main shaft and the bearing member are abruptly worn. In order to enhance the precision of the lap, it is necessary to precisely machine the mounting surface and the sliding surface, but since the cutting performance of the iron-based material is low, it is extremely difficult to machine the iron-based material, and it is difficult to enhance the productivity.
If each of the compression chambers is compressed, compression heat is generated, and each scroll part is heated to high temperature due to this heat. The pressure in the compression chambers is gradually increased from the most outer peripheral compression chamber toward the center compression chamber, and temperature gradient is generated from the most outer peripheral side toward the center in the lap. That is, the temperature of the center side (most inner peripheral side) compression chamber becomes higher than that of the most outer peripheral compression chamber. The lap is thermally expanded due to this temperature rise, and especially the inner peripheral side of the lap located on the central side where the temperature is increased is largely thermally expanded. For this reason, when the lap is thermally expanded, a gap in the thrust direction between teeth tips of the lap and teeth bottoms of the mirror plates becomes smaller than a gap at the time of assembling operation, and teeth tips of the lap come into contact with the teeth bottoms of the mirror plates. If the contact surface pressure is further increased, there is a fear that galling is generated therebetween, the mirror plates and the lap are damaged, and there is a problem that the compression efficiency and durability of the compressor are deteriorated. Especially when iron-based material is used for the fixed scroll part, aluminum-based material is used for the orbiting scroll part and metals having different coefficient of thermal expansion are used, this problem appears seriously.
If one or both of the orbiting scroll part and fixed scroll part are provided with chip seals to avoid the performance deterioration caused by the thrust direction gap, there is a problem that the chip seals are contacted, the sliding loss is increased, the number of parts is increased, the number of machining steps is increased and the productivity is deteriorated.
Hence, it is another object of the present invention to provide an efficient and reliable scroll compressor when carbon dioxide is used as a refrigerant.
In the scroll compressor described in patent document 2, each compression chamber formed between the fixed scroll part and the orbiting scroll part is thermally expanded due to compression heat caused by compression, and this fact is taken into consideration. However, deformations of the fixed scroll part and orbiting scroll part caused by pressure difference between the discharge pressure and the suction pressure of the compressor are not taken into consideration. Especially in the housing of an eccentric bearing in the orbiting scroll part, the thickness of the mirror plate of the orbiting scroll part is thin, the deformation toward the fixed scroll part is large due to the pressure difference between the discharge pressure and the suction pressure, the teeth bottoms of the orbiting scroll and the teeth tips of the fixed scroll eccentrically abut against each other, the contact surface pressure is increased, galling is generated therebetween, and there is a problem that the compression efficiency and durability of the compressor are deteriorated.
Hence, it is another object of the present invention to provide a reliable scroll compressor realizing high efficiency from the initial stage of operation while taking the pressure deformation in the housing of the eccentric bearing in the orbiting scroll is taken into consideration.